Acceleration sensors have been used for hard disc drives to detect stress caused by external impact and vibration applied to the hard disc drives.
Various structures have been proposed for an acceleration sensor according to the use thereof. One known example of acceleration sensor with relatively high detection sensitivity is an acceleration sensor with a cantilever structure including an oscillation detecting element whose one end portion is held while the other end portion is free (e.g. Patent Document 1).
The foregoing conventional acceleration sensor is arranged such that a side surface of a holding member in the form of a rectangular parallelepiped is provided with a lateral hole and the upper surface thereof is provided with a vertical hole that is communicated with the lateral hole, and an oscillation detecting element is inserted into the lateral hole and tentatively fixed, then after supporting resin is injected through the vertical hole to cure the resin so as to hold one end portion of the oscillation detecting element.
The holding member that holds the oscillation detecting element is mounted on a metal case, and the oscillation detecting element, holding member and metal case are accommodated in a case made of resin.
When acceleration generated by impact or the like is applied to such an acceleration sensor, the oscillation detecting element bends to cause deformation of a piezoelectric substrate constituting the oscillation detecting element.
An electric charge is generated by the piezoelectric effect in the deformed piezoelectric substrate, which further causes a potential difference between the signal electrodes formed on both principal surfaces of the piezoelectric substrate. Acceleration is detected from detecting a voltage obtained by this potential difference. Patent Document 1: Japanese Unexamined Patent Publication No. 9-113533